1. Field of the Invention
The present invention relates to power systems and methods designed for the utilization of heat sources with high or medium initial temperatures (from 1076° F. to 400° F.) in medium and small scale power plants.
More particularly, the present invention relates to power systems and methods designed for the utilization of heat sources with high or medium initial temperatures (from 1076° F. to 400° F.) in medium and small scale power plants, where the systems include complete at least one turbine, six heat exchange apparatus, a heat recovery vapor generator, at least three working fluid pumps, a separator and optionally an admission valve along with a plurality of mixing and dividing valves. The method includes converting a portion of heat in at least one vaporized, superheated working fluid stream, using a spent stream to heat a rich or basic working fluid stream and lean working fluid stream, combining the cooled superheated stream with a portion of the lean stream and using the combined stream to preheat the rich working fluid stream and the lean working fluid stream and separating a resulting partially condensed combined stream into a vapor stream and a lean working fluid liquid stream, forming the basic working fluid stream from the vapor stream and a portion of the lean working fluid liquid stream, where the cycle is closed and an external coolant stream is used to condense the basic working fluid stream and an external heat source stream is used to fully vaporize and superheat the at least one working fluid stream prior to the converting step.
2. Description of the Related Art
In U.S. Pat. Nos. 5,095,708, and 5,572,871, power systems were presented that were designed to serve as bottoming cycles for combined cycle systems. These systems both had a specific feature which was the key to their high efficiency; both systems used intercooling of the working fluid in between turbine stages. Because the heat released during intercooling was recuperated, it was then used as an additional source of heating for the process of vaporization. This resulted in a drastic increase in the thermodynamical reversibility and correspondingly in higher efficiency of the power cycle.
However, in the prior art, this process of intercooling was performed in a special heat exchanger, a so-called “intercooler.” Such an intercooler requires that the streams of working fluid in both the tubes and the shell of the intercooler be at high pressure. Moreover, the intercooled stream in the prior art is in the form of a vapor, and therefore the heat transfer coefficient from the vapor to the intercooler tubes is low. As a result, such an intercooler must be a very large and very expensive high pressure heat exchanger. This in turn has a very negative impact on the economics of the entire system.
Thus, there is a need in the art for a system designed to utilize high to medium temperatures sources in small to medium power plants to convert a portion of the thermal energy from these heat sources into electrical power.